Many landfills and processing facilities are experiencing higher H2S concentrations in their gas. Many times, this gas needs to be cleaned of the H2S. One process for achieving this is through the use of a solid H2S Scavenger System (Graubard, D. et al. (2010), “Cost-Effective Technologies for Removing H2S from Landfill Gas,” (http://www.merichem.com/resources/technical_papers/landfill_gas_technologies/index.php). Typical gas scrubbing media consists of a ceramic base that is impregnated with iron oxide (Fe2O3). When the water-saturated gas containing H2S comes in contact with the media, the H2S is converted to Iron Pyrite (FeS2). As disclosed in Graubard et al, in a typical solid media system in a tank, the gas passes in a down-flow direction. Sour gas enters at the top of the tank and sweet or cleaned gas exits the system at the bottom of the tank. Systems are designed for either batch processing (single vessel) or Lead-Lag operation (two vessels) that allows for continuous treatment of the H2S.
Typical processing tanks in the prior art are large, approximately 10 feet in height and 8 feet in diameter. At the bottom of the tank are rocks on top of which rests a foam pad and then a gas scrubbing medium.
A preferred gas scrubbing medium is called SULFATREAT® (SulfaTreat, a business unit of M-I, LLC, Chesterfield, Mo.). Reference is made to the following website for a more information: www.sulfatreat.com. The SULFATREAT® medium is a granular material used for cleaning gasses and specifically used in the removal of H2S from gas streams, typically through a batch-processing treatment. It is typically prepared by placing the medium in a large receptacle or bag (often called a “Super Sack”), which is approximately 3 by 3 by 3½ feet tall and weighs approximately 2000 pounds.
A typical tank in the prior art will hold up to 16,000 pounds of gas scrubbing media (or eight bags of the SULFATREAT® media). The bags used for the SULFATREAT® media are typically made of coated black ultraviolet (UV) treated circular woven polypropylene. The tank includes access openings (or manways) usually at the top and side (near the bottom) of the tank. In operation, sour or raw gas enters the headspace near the top of the tank, flows through the SULFATREAT® media, then a foam pad, and then the rocks and out near the bottom as clean gas. The amount of cleaning depends in part on the level of incoming H2S or contaminant level and the condition of the media, i.e., how long it has been in cleaning operation.
Media change-out can be a messy operation with high pressure water hoses required to cut the spent material out of the vessel.
The following operations occur during change out:                1. The gas cleaning system is shut down, and the container is isolated and purged such that all H2S and other gaseous contaminants are removed from the container and to avoid the possibility of raw or sour gas entering the container while it is being serviced;        2. All inlet and outlet ports and piping are purged;        3. The top manway is opened and removed;        4. Water is added to fill the container to control dust and/or any heating, then drained;        5. The tank is thoroughly vacuumed;        6. A hammer, shovel, pick, and/or water pick is used as necessary to break loose material from the inner walls of the tank. The material is vacuumed as it breaks loose;        7. The bottom manway is opened to enable further cleaning and removal of spent scrubbing medium;        8. The old foam pad is removed;        9. A new foam pad is inserted;        10. Both manways are closed;        11. A pressure test is conducted;        12. The top manway is opened;        13. A forklift is used to bring bags of clean scrubbing media to a crane;        14. The crane lifts the bags above the top manway;        15. The bag is opened;        16. The scrubbing medium is drained from the bag into the tank;        17. The crane removes the empty bag;        18. The empty bag is taken to a landfill;        19. This process is repeated until approximately eight bags or 16,000 pounds of scrubbing media have been loaded into the polishing tank;        20. A rake or similar device is used to level out the media in the polishing tank;        21. The manway is closed;        22. The tank is pressure tested;        23. The tank is then run; and        24. The spent media is taken in a vacuum truck (with empty bags) to a landfill.        
There are some significant problems with the current system.
First, it is very costly. Initial costs to install the tanks are high and, more importantly, the operating costs are extremely high.
Second, it is also a very dirty manually intensive job.
Third, it requires some large and unique equipment, such as an environmentally sanctioned vacuum truck, a crane or similar device, and a vehicle to get spent media to landfill.
Fourth, there is a significant time commitment. Under good circumstances, the change out process could take a full day's work for 2 to 4 people.
Fifth, the process requires coordination to be able to determine the best time to have the media changed.
Thus, there is needed another more economical system.